Minimally invasive surgery is surgery performed with only a small incision or no incision at all and is typically performed with an endoscope, bronchoscope, laparoscope, or like instrument.
In a bronchoscopic procedure, for example, a bronchoscope is inserted through the nose or mouth of the patient, advanced through the trachea and into a desired airway. The surgery may then be performed through the working lumen of the bronchoscope. A light source and camera at the tip of the bronchoscope enables the physician to observe the airway wall in real time. A skilled physician can identify his location along the airway and navigate to the desired location along the airway wall.
It is often desirable, however, to supplement endoscopic visualization with radiological guidance (e.g., by taking real time X-ray images of the region with a fluoroscope). In certain procedures radiologic guidance is necessary.
In a transbronchial needle aspiration (TBNA) procedure, for example, a long flexible catheter comprising a needle at the tip is advanced through the working lumen of the bronchoscope to the target site. The needle is then advanced through the airway wall outside of view of the bronchoscope to aspirate a sample of tissue. It is highly desirable or necessary to have fluoroscopy or an alternative means to view and track the needle once it is outside of view of the bronchoscope.
Tracking devices using a fluoroscope, however, is not straightforward. To track a device, multiple 2D X-ray images from multiple different fluoroscopic camera views are taken. Based on the information provided by these two images, the physician determines the position of the device. Determining the position based on two 2D X-rays relies on the skill and experience of the physician. Even for the most skilled physicians there is a considerable degree of uncertainty. This is undesirable.
One approach to address the above mentioned problem is described in US Patent Publication No. 2003/0181809 to Hall et al. (hereinafter referred to as “the Hall Publication”). The Hall Publication describes a method of visualizing a surgical instrument that has been introduced into an area of examination within a patient, in particular a catheter that is used during a cardiological examination or treatment, comprising the following steps: using a 3D image data set of the area of examination and generating a 3D reconstructed image of the area of examination, taking at least one 2D X-ray image of the area of examination in which the instrument is visualized, registering the 3D reconstructed image relative to the 2D X-ray image, and visualizing the 3D reconstructed image and superimposing the 2D X-ray image over the 3D reconstructed image on a monitor.
Although the Hall Publication addresses visualization of the heart and central vasculature tree using a rigid registration technique, and compensates for the rhythmatic motion of the heart, the Hall Publication does not appear to address body organ applications in which the shape and position of the body organ is affected by the position or posture of the patient. In such unfixed or non-rigid body organ applications, it is difficult to visualize the non-rigid body organs because the position (or posture) of the patient's body during the pre-operative image scans may be substantially different than his position during the surgical procedure. Although this is of no consequence for certain organs that are generally rigid in one body position or another such as the heart, spine and brain, a change in patient position for non-rigid body organs presents a challenge because previously acquired 3D image data and the 3D model arising there from will not match the real-time image organ data. In addition to the difference in posture/position of the patient, the “static” pre-operative scans may also differ from the real-time “moving” images due to the motion induced by breathing. Stated another way, the shape of the organ from the pre-operative scans shall not match the shape of the organ during the procedure. This thwarts live tracking and guidance.
A method and system to assist surgeons to track surgical devices in a body organ, that has application to non-rigid organs such as the lung, and that does not suffer the above identified drawbacks is therefore desired.